Carbon ceramic electrodes modified with mixed oxides SiO<Subscript>2</Subscript>/SnO<Subscript>2</Subscript> for determination of levofloxacin

The preparation of a carbon ceramic electrode modified with SnO₂ (CCE/SnO₂) using tin dibutyl diacetate as precursor was optimized by a 2³ factorial design. The factors analyzed were catalyst (HCl), graphite/organic precursor ratio, and inorganic precursor (dibutyltin diacetate). The statistical treatment of the data showed that only the second-order interaction effect, catalyst × inorganic precursor, was significant at 95% confidence level, for the electrochemical response of the system. The obtained material was characterized by scanning electron microscopy (MEV), X-ray diffraction (XRD), RAMAN spectroscopy, XPS spectra, and voltammetric techniques. From the XPS spectra, it was confirmed the formation of the Si–O–Sn bond by the shift in the binding energy values referred to Sn 3d3/2 due to the interaction of Sn with SiOH species. The incorporation of SnO₂ provided an increment of the electrode response for levofloxacin, with Ipa = 147.0 μA for the ECC and Ipa = 228.8 μA for ECC/SnO₂, indicating that SnO₂ when incorporated into the silica network enhances the electron transfer process. Under the optimized working conditions, the peak current increased linearly with the levofloxacin concentration in the range from 6.21×10^?5 to 6.97×10^?4 mol L^?1 with quantification and detection limits of 3.80×10^?5 mol L^?1 (14.07 mg L^?1) and 1.13×10^?5 mol L^?1 (4.18 mg L^?1), respectively.     

Synthesis and thermal decomposition of neodymium(III) peroxotitanate to Nd<Subscript>2</Subscript>TiO<Subscript>5</Subscript>

Neodymium(III) peroxotitanate is used as a precursor for obtaining Nd₂TiO₅. The last one possesses numerous valuable electrophysical properties. TiCl₄, Nd(NO₃)₃·6H₂O and H₂O₂ in mol ratio 1:2:10 were used as starting materials. The reaction ambience was alkalized to pH = 9 with a solution of NH₃. The obtained neodymium(III) peroxotitanate and intermediate compounds of the isothermal heating were proved by the help of quantitative analysis and infrared spectroscopy (IRS). It has Nd₄[Ti₂(O₂)₄(OH)₁₂]·7H₂O composition. The absorption band observed in IRS at 831 cm^?1 relates to a triangular bonding of the peroxo group of Ti, at 1062 cm^?1—terminal groups Ti–OH and at 1491 and 1384 cm^?1—the bridging OH^?-groups Ti–O(H)–Ti. Nd₂TiO₅ was obtained by thermal decomposition of neodymium(III) peroxotitanate. The isothermal conditions for decomposition were determined on the base of differential thermal analysis, thermogravimetric and differential scanning calorimetry results in the temperature range of 20–1000 °C. The mechanism of thermal decomposition of Nd₄[Ti₂(O₂)₄(OH)₁₂]·7H₂O to Nd₂TiO₅ was studied. In the temperature range of 20–208 °C, a simultaneous decomposition of the peroxo groups by the separation of oxygen and hydrate water is conducted and Nd₄[Ti₂O₄(OH)₁₂] is obtained. From 208 to 390 °C, the terminal OH^?-groups are separated and Nd₄[Ti₂O₇(OH)₆] is formed. In the range of 390–824 °C, the bridging OH^?-groups are completely decomposed to Nd₂TiO₅. The optimal conditions for obtaining nanocrystalline Nd₂TiO₅ are 900 °C for 6 h and 20–80 nm.     

4-(Methylsulfonyl)benzaldehyde Solubility in Binary Solvent Mixtures of Acetonitrile + (Methanol,Ethanol and Isopropanol): Determination and Modelling

The solubilities of 4-(methylsulfonyl)benzaldehyde in the binary mixed solvents acetonitrile + methanol, acetonitrile + ethanol and acetonitrile + isopropanol were determined experimentally using an isothermal dissolution equilibrium method within the temperature range from 283.15 to 318.15 K under atmospheric pressure. The solubility of 4-(methylsulfonyl)benzaldehyde increased with increasing temperature and mass fraction of acetonitrile in each binary system. At the same temperature and mass fraction of acetonitrile, the mole fraction solubility of 4-(methylsulfonyl)benzaldehyde is greater in (acetonitrile + methanol) than in the other two mixed solvents. The solubility data were correlated using the CNIBS/R-K model, Jouyban–Acree model, van’t Hoff–Jouyban–Acree model, Apelblat–Jouyban–Acree model, Ma model and Sun model. The maximum values of relative average deviation (RAD) and root-mean-square deviation (RMSD) are 1.53% and 1.17 × 10^?4, respectively. All of the selected models provided good representation of the experimental solubilities. Furthermore, the standard enthalpies of dissolution were calculated. The dissolution process for 4-(methylsulfonyl)benzaldehyde in these mixed solvents is endothermic. The experimental solubility and the models presented in this work are important for the production and purification of 4-(methylsulfonyl)benzaldehyde.     

Equilibrium isotherms and isosteric heat for CO<Subscript>2</Subscript> adsorption on nanoporous carbons from polymers

Four nanoporous carbons obtained from different polymers: polypyrrole, polyvinylidene fluoride, sulfonated styrene–divinylbenzene resin, and phenol–formaldehyde resin, were investigated as potential adsorbents for carbon dioxide. CO₂ adsorption isotherms measured at eight temperatures between 0 and 60 °C were used to study adsorption properties of these polymer-derived carbons, especially CO₂ uptakes at ambient pressure and different temperatures, working capacity, and isosteric heat of adsorption. The specific surface areas and the volumes of micropores and ultramicropores estimated for these materials by using the density functional theory-based software for pore size analysis ranged from 840 to 1990 m² g^?1, from 0.22 to 1.47 cm³ g^?1, and from 0.18 to 0.64 cm³ g^?1, respectively. The observed differences in the nanoporosity of these carbons had a pronounced effect on the CO₂ adsorption properties. The highest CO₂ uptakes, 6.92 mmol g^?1 (0 °C, 1 atm) and 1.89 mmol g^?1 (60 °C, 1 atm), were obtained for the polypyrrole-derived activated carbon prepared through a single carbonization-KOH activation step. The working capacity for this adsorbent was estimated to be 3.70 mmol g^?1. Depending on the adsorbent, the CO₂ isosteric heats of adsorption varied from 32.9 to 16.3 kJ mol^?1 in 0–2.5 mmol g^?1 range. Overall, the carbons studied showed well-developed microporosity and exceptional CO₂ adsorption, which make them viable candidates for CO₂ capture, and for other adsorption and environmental-related applications.     

Layered LiNi<Subscript>0.80</Subscript>Co<Subscript>0.15</Subscript>Al<Subscript>0.05</Subscript>O<Subscript>2</Subscript> as cathode material for hybrid Li<Superscript>+</Superscript>/Na<Superscript>+</Superscript> batteries

LiNi_0.80Co_0.15Al_0.05O₂ (NCA) is explored to be applied in a hybrid Li⁺/Na⁺ battery for the first time. The cell is constructed with NCA as the positive electrode, sodium metal as the negative electrode, and 1 M NaClO₄ solution as the electrolyte. It is found that during electrochemical cycling both Na⁺ and Li⁺ ions are reversibly intercalated into/de-intercalated from NCA crystal lattice. The detailed electrochemical process is systematically investigated by inductively coupled plasma-optical emission spectrometry, ex situ X-ray diffraction, scanning electron microscopy, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy. The NCA cathode can deliver initially a high capacity up to 174 mAh g^?1 and 95% coulombic efficiency under 0.1 C (1 C?=?120 mA g^?1) current rate between 1.5–4.1 V. It also shows excellent rate capability that reaches 92 mAh g^?1 at 10 C. Furthermore, this hybrid battery displays superior long-term cycle life with a capacity retention of 81% after 300 cycles in the voltage range from 2.0 to 4.0 V, offering a promising application in energy storage.     

Measurement and correlation of antifungal drugs solubility in pure supercritical CO2 using semiempirical models

In the present study the solubilities of two antifungal drugs of ketoconazole and clotrimazole in supercritical carbon dioxide were measured using a simple static method. The experimental data were measured at (308 to 348) K, over the pressure range of (12.2 to 35.5) MPa. The mole fraction solubilities ranged from 0.2 · 10^?6 to 17.45 · 10^?5. In this study five density based models were used to calculate the solubility of drugs in supercritical carbon dioxide. The density based models are Chrastil, modified Chrastil, Bartle, modified Bartle and Mendez-Santiago and Teja (M–T). Interaction parameters for the studied models were obtained and the percentage of average absolute relative deviation (AARD%) in each calculation was displayed. The correlation results showed good agreement with the experimental data. A comparison among the five models revealed that the Bartle and its modified models gave much better correlations of the solubility data with an average absolute relative deviation (AARD%) ranging from 4.8% to 6.2% and from 4.5% to 6.3% for ketoconazole and clotrimazole, respectively. Using the correlation results, the heat of drug–CO₂ solvation and that of drug vaporization was separately approximated in the range of (?22.1 to ?26.4 and 88.3 to 125.9) kJ · mol^?1.     

Functionalized MgO,CeO<Subscript>2</Subscript> and ZnO nanoparticles with humic acid for the study of nitrate adsorption efficiency from water

In this study, the removal of nitrate using ZnO, MgO, and CeO₂ nanoparticles (NPs) modified by humic acid from water was tested. Nanoparticles were modified by humic acid using the microwave-assisted technique and then modified ZnO (Zn–H), modified MgO (Mg–H), and modified CeO₂ (Ce–H) were characterized through SEM, EDX, FTIR, and XRD analysis. Several important parameters influencing the removal of nitrate such as contact time, pH, adsorbent dosage and temperature were explored systematically by batch experiments. Isotherm studies were set up with the following optimum conditions: pH?=?5, adsorbent concentration of 1 g L^?1, 180 min and 25 °C. The results revealed that the adsorption were best fitted to pseudo-second order and simple Elovich kinetics models. Langmuir, Freundlich and linear adsorption models were fitted to describe adsorption isotherms and constants. The isotherm analysis indicated that the adsorption data can be represented by both Freundlich and linear isotherm models. The maximum adsorption capacity (q_m) was obtained at 55.1, 74.2 and 75.8 mg g^?1 for Zn–H, Ce–H, and Mg–H, respectively. The thermodynamic parameters such as free energy, enthalpy and entropy of adsorption were obtained. From the thermodynamic parameters, it is suggested that the adsorption of nitrate on modified NPs (MNPs) followed the exothermic and spontaneous processes. The obtained results showed that the MNPs were efficient adsorbents for removing nitrate from aqueous media.     

Correlation between the structural,electrical and electrochemical performance of layered Li(Ni<Subscript>0.33</Subscript>Co<Subscript>0.33</Subscript>Mn<Subscript>0.33</Subscript>)O<Subscript>2</Subscript> for lithium ion battery

The Li(Ni_0.33Co_0.33Mn_0.33)O₂ (LNCMO) cathode material is prepared by poly(vinyl pyrrolidone) (PVP)-assisted sol-gel/hydrothermal and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly (ethylene glycol) (Pluronic-P123)-assisted hydrothermal methods. The compound prepared by PVP-assisted hydrothermal method shows a comparatively higher electrical conductivity of ~2?×?10^?5 S cm^?1 and exhibits a discharge capacity of 152 mAh g^?1 in the voltage range of 2.5 to 4.4 V, for a C-rate of 0.2 C, whereas the compounds prepared by P123-assisted hydrothermal method and PVP-assisted sol-gel method show a total electrical conductivity in the order of 10^?6 S cm^?1 and result in poor electrochemical performance. The structural and electrical properties of LNCMO (active material) and its electrochemical performance are correlated. The difference in percentage of ionic and electronic conductivity contribution to the total electrical conductivity is compared by transference number studies. The cation disorder is found to be the limiting factor for the lithium ion diffusion as determined from ionic conductivity values.     

LiMO<Subscript>2</Subscript>@Li<Subscript>2</Subscript>MnO<Subscript>3</Subscript> positive-electrode material for high energy density lithium ion batteries

Li[Ni_1/3Co_1/3Mn_1/3]O₂ (NCM 111) is a promising alternative to LiCoO₂, as it is less expensive, more structurally stable, and has better safety characteristics. However, its capacity of 155 mAh g^?1 is quite low, and cycling at potentials above 4.5 V leads to rapid capacity deterioration. Here, we report a successful synthesis of lithium-rich layered oxides (LLOs) with a core of LiMO₂ (R-3m, M?=?Ni, Co) and a shell of Li₂MnO₃ (C2/m) (the molar ratio of Ni, Co to Mn is the same as that in NCM 111). The core–shell structure of these LLOs was confirmed by XRD, TEM, and XPS. The Rietveld refinement data showed that these LLOs possess less Li⁺/Ni²⁺ cation disorder and stronger M*–O (M*?=?Mn, Co, Ni) bonds than NCM 111. The core–shell material Li_1.15Na_0.5(Ni_1/3Co_1/3)_core(Mn_1/3)_shellO₂ can be cycled to a high upper cutoff potential of 4.7 V, delivers a high discharge capacity of 218 mAh g^?1 at 20 mA g^?1, and retains 90 % of its discharge capacity at 100 mA g^?1 after 90 cycles; thus, the use of this material in lithium ion batteries could substantially increase their energy density.

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Graphical Abstract Average voltage vs. number of cycles for the core–shell and pristine materials at 20 mA g^?1 for 10 cycles followed by 90 cycles at 100 mA g^?1

     

Evaluation of thermal stability and parameters of dissolution of nifedipine crystals

Nifedipine is a calcium channel blocker as well as a powerful vasodilator used to treat ischemic heart disease and hypertension. Its photosensitivity and very low solubility in water have been widely acknowledged as important properties deserving improvements. The main thrust of this study is to characterize the nature and the solid-state of nifedipine crystals obtained using different solvents as well as assess the stability by thermal methods (TG and DSC) and crystals structure by means of spectroscopic techniques (MID FTIR and XRD) and assess the dissolution parameters for such crystals. The calculated kinetic parameters activation energy (E _a = 123.3 kJ mol^?1 ± 0.1), the factor frequency (A = 25.93 ± 0.9 min^?1), and the reaction order (n = 0.2) of the main stage of thermal decomposition of nifedipine raw material were performed according to the Ozawa model. The data showed a zero-order kinetic behavior for all crystals despite the different values of E _a and A. The dissolution profiles were obtained for such crystals in three dissolution media with different pH values. After 1 h of dissolution, the higher amount of nifedipine dissolved was observed for crystals obtained in isopropyl alcohol (52.5 %, pH 4.5), followed by those in chloroform (48.1 %, pH 1.2) and subsequently in acetone (32.5 %, pH 6.8). Results showed different thermal stabilities and significant variations in the solubility of the crystals.     

Photo-fenton refreshable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@HCS adsorbent for the elimination of tetracycline hydrochloride

A yolk–shell-structured sphere composed of a superparamagnetic Fe₃O₄ core and a carbon shell (Fe₃O₄@HCS) was etched from Fe₃O₄@SiO₂@carbon by NaOH, which was synthesized through the layer-by-layer coating of Fe₃O₄. This yolk–shell composite has a shell thickness of ca. 27 nm and a high specific surface area of 213.2 m² g^?1. Its performance for the magnetic removal of tetracycline hydrochloride from water was systematically examined. A high equilibrium adsorption capacity of ca. 49.0 mg g^?1 was determined. Moreover, the adsorbent can be regenerated within 10 min through a photo-Fenton reaction. A stable adsorption capacity of 44.3 mg g^?1 with a fluctuation <10% is preserved after 5 consecutive adsorption–degradation cycles, demonstrating its promising application potential in the decontamination of sewage water polluted by antibiotics.     

Stability-Indicating LC Method for the Determination of Lacidipine in Tablets. Application to Degradation Kinetics and Content Uniformity Testing

A simple, stability-indicating, reversed-phase liquid chromatographic method was developed for the determination of lacidipine in the presence of its degradation products. The analysis was carried out using a 150 mm × 4.6 mm i.d., 5 μm particle size Nucleodur MN-C18 column. Mobile phase containing a mixture of acetonitrile and 0.02 M phosphate buffer (70:30) at pH = 5.0 was pumped at a flow rate of 1 mL min^?1 with UV-detection at 254 nm. The method showed good linearity in the range of 0.06–15 μg mL^?1 with a limit of detection (S/N = 3) of 0.016 μg mL^?1 (3.5 × 10^?8 M). The suggested method was successfully applied for the analysis of lacidipine in bulk and in commercial tablets with average recoveries of 100.19 ± 0.81% and 100.05 ± 0.69%, respectively. The results were favorably compared to those obtained by a reference method. The suggested method was utilized to investigate the kinetics of alkaline, acidic, peroxide and photo-induced degradation of the drug. The apparent first-order rate constant, half-life times and activation energies of the degradation process were calculated. The pH profile curve was derived. The proposed method was successfully applied to the content uniformity testing of tablets.     

Mechanical and optical properties of SiO<Subscript>2</Subscript> thin films deposited on glass

The optical and mechanical properties of amorphous SiO₂ films deposited on soda-lime silicate float glass by reactive RF magnetron sputtering at room temperature were investigated in dependence of the process pressure. The densities of the films are strongly influenced by the process pressure and vary between 2.38 and 1.91 g cm^?3 as the pressure changes from 0.27 to 1.33 Pa. The refractive indices of the films shift between 1.52 and 1.37, while the residual compressive stresses in the deposited films vary in the range from 440 to 1 MPa. Hardness and reduced elastic modulus values follow the same trend and decline with the increase of process pressure from 8.5 to 2.2 GPa and from 73.7 to 30.9 GPa, respectively. The abrasive wear resistance decreases with the density of the films.     

High-Pressure Solubility of l-Methionine in Water

The solubility (m _S) of l-methionine in water was measured at 298.2 K and pressures up to 200 MPa. The data were fitted to the equation ln(m _S/mol·kg^?1) = ?4.62 × 10^?6 (p/MPa)² + 2.65 × 10^?3 (p/MPa) ? 0.970 with a standard deviation of σ(ln m _S) = 0.002. The pressure coefficient of the logarithm of solubility (?ln m _S/?p) _T was thermodynamically estimated to be (2.62 ± 0.34) × 10^?3 MPa^?1 at 0.10 MPa using several parameters such as partial molar volume and activity coefficient of l-methionine in water and molar volume of solid l-methionine. The resulting value agrees well with the second term on the right-hand side of the fitted equation above, indicating the reliability of the high-pressure solubility measurements. The value of (?ln m _S/?p) _T also was compared with those of other amino acids.     

Carbon paste electrode modified with Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles and BMI.PF<Subscript>6</Subscript> ionic liquid for determination of estrone by square-wave voltammetry

A carbon paste electrode (CPE) modified with Fe₃O₄ nanoparticles (Fe₃O₄ NP) and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (IL BMI.PF₆) was employed for the electroanalytical determination of estrone (E1) by square-wave voltammetry (SWV). At the modified electrode, cyclic voltammograms of E1 in B–R buffer (pH 12.0) showed an adsorption-controlled irreversible oxidation peak at around +0.365 V. The anodic current increased by a factor of five times and the peak potential shifted 65 mV to less positive values compared with the unmodified CPE. Under optimized conditions, the calibration curve obtained showed two linear ranges: from 4.0 to 9.0 μmol L^?1 and from 9.0 to 100.0 μmol L^?1. The limits of detection (LOD) and quantification (LOQ) attained were 0.47 and 4.0 μmol L^?1, respectively. The proposed modified electrode was applied to the determination of E1 in pork meat samples. Data provided by the proposed modified electrode were compared with data obtained by UV–vis spectroscopy. The outstanding performance of the electrochemical device indicates that Fe₃O₄ NP and the IL BMI.PF₆ are promising materials for the preparation of chemically modified electrodes for the determination of E1.     

Electrochemical performance of novel Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> glass-ceramic nanocomposites as electrodes for energy storage devices

The novel Li₃V₂(PO₄)₃ glass-ceramic nanocomposites were synthesized and investigated as electrodes for energy storage devices. They were fabricated by heat treatment (HT) of 37.5Li₂O–25V₂O₅–37.5P₂O₅?mol% glass at 450 °C for different times in the air. XRD, SEM, and electrochemical methods were used to study the effect of HT time on the nanostructure and electrochemical performance for Li₃V₂(PO₄)₃ glass-ceramic nanocomposites electrodes. XRD patterns showed forming Li₃V₂(PO₄)₃ NASICON type with monoclinic structure. The crystalline sizes were found to be in the range of 32–56 nm. SEM morphologies exhibited non-uniform grains and changed with variation of HT time. The electrochemical performance of Li₃V₂(PO₄)₃ glass-ceramic nanocomposites was investigated by using galvanostatic charge/discharge methods, cyclic voltammetry, and electrochemical impedance spectroscopy in 1 M H₂SO₄ aqueous electrolyte. The glass-ceramic nanocomposites annealed for 4 h, which had a lower crystalline size, exhibited the best electrochemical performance with a specific capacity of 116.4 F g^?1 at 0.5 A g^?1. Small crystalline size supported the lithium ion mobility in the electrode by decreasing the ion diffusion pathway. Therefore, the Li₃V₂(PO₄)₃ glass-ceramic nanocomposites can be promising candidates for large-scale industrial applications in high-performance energy storage devices.     

Solid–Liquid Equilibrium for the Ternary System 2-Methyl-4-Nitroaniline + 2-Methyl-6-Nitroaniline + Ethyl Acetate: Determination and Modelling

The solid–liquid phase equilibria for the ternary system 2-methyl-4-nitroaniline + 2-methyl-6-nitroaniline + ethyl acetate was determined experimentally by the method of isothermal solution saturation at temperatures of (293.15, 303.15 and 313.15) K under the pressure of 101.2 kPa. Based on the obtained solubility data, the isothermal phase diagrams of the system were constructed. At each temperature, there are two pure solid phases formed, which correspond to pure 2-methyl-4-nitroaniline and pure 2-methyl-6-nitroaniline, which was confirmed by Schreinemakers’ wet residue method and X-ray powder diffraction. The crystallization regions of pure 2-methyl-4-nitroaniline and pure 2-methyl-6-nitroaniline increased with decreasing temperature. The crystalline region of 2-methyl-4-nitroaniline was larger than that of 2-methyl-6-nitroaniline at a fixed temperature. The solubility data were correlated with the NRTL and Wilson models. The values of the root-mean-square deviations are 5.01 × 10^?3 for the NRTL model, and 6.43 × 10^?3 for the Wilson model. The solid–liquid equilibria, phase diagrams and the thermodynamic models for the ternary system can provide the foundation for separating 2-methyl-6-nitroaniline or 2-methyl-4-nitroaniline from its mixtures.     

Graphene oxide/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@polythionine nanocomposite as an efficient sorbent for magnetic solid-phase extraction followed by high-performance liquid chromatography for the determination of duloxetine in human plasma

Herein, an efficient graphene oxide/Fe₃O₄@polythionine (GO/Fe₃O₄/PTh) nanocomposite sorbent was introduced for magnetic solid-phase extraction combined with high-performance liquid chromatography–ultraviolet detection of duloxetine (DLX) in human plasma. To prepare the sorbent, an oxidative polymerization of thionine on the surface of magnetic GO was utilized while PTh was simply used as a surface modifier to improve extraction efficiency. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, vibrating sample magnetometry, Fourier transform-infrared spectroscopy and Brunauer–Emmett–Teller technique were applied to characterize the prepared nanoparticles. Firstly, effective parameters controlling the performance of the extraction process were evaluated in detail and optimized. Under the optimized conditions, calibration curve showed linearity in the range of 2–2500 ng mL^?1 with regression coefficient corresponding to 0.998. Limits of detection (LOD, S/N = 3) and quantification (LOQ, S/N = 10) were 0.5 and 2 ng mL^?1, respectively. Reasonable intra-assay (3.5–4.5%, n = 6) and inter-assay (3.8–6.7%, n = 9) precision represented acceptable performance of the procedure. The applicability of the method was successfully extended to the determination of DLX in human plasma after oral administration of 60 mg single dose of the drug and finally some pharmacokinetic data was achieved.     

Fabrication of a New Self-assembly Compound of CsTi<Subscript>2</Subscript>NbO<Subscript>7</Subscript> with Cationic Cobalt Porphyrin Utilized as an Ascorbic Acid Sensor

A novel sandwich-structured nanocomposite based on Ti₂NbO₇^? nanosheets and cobalt porphyrin (CoTMPyP) was fabricated through electrostatic interaction, in which CoTMPyP has been successfully inserted into the lamellar spacing of layered titanoniobate. The resultant Ti₂NbO₇/CoTMPyP nanocomposite was characterized by XRD, SEM, TEM, EDS, FT-IR, and UV-vis. It is demonstrated that the intercalated CoTMPyP molecules were found to be tilted approximately 63° against Ti₂NbO₇^? layers. The glass carbon electrode (GCE) modified by Ti₂NbO₇/CoTMPyP film showed a fine diffusion-controlled electrochemical redox process. Furthermore, the Ti₂NbO₇/CoTMPyP-modified electrode exhibited excellent electrocatalytic oxidation activity of ascorbic acid (AA). Differential pulse voltammetric studies demonstrated that the intercalated nanocomposite detects AA linearly over a concentration range of 4.99?×?10^?5 to 9.95?×?10^?4 mol L^?1 with a detection limit of 3.1?×?10^?5 mol L^?1 at a signal-to-noise ratio of 3.0.     

The <Emphasis Type="Italic">r</Emphasis><Subscript>0</Subscript> structural parameters of equatorial and axial chlorocyclobutane,conformational stability from temperature dependent infrared spectra of xenon solutions,and vibrational assignments

Variable temperature (?55 to ?100 °C) studies of the infrared spectra (4,000–400 cm^?1) of chlorocyclobutane, c-C₄H₇Cl, dissolved in liquid xenon have been carried out. The infrared spectrum (4,000–100 cm^–1) of the gas has also been recorded. For this puckered ring molecule the enthalpy difference between the more stable equatorial conformer and the axial form, has been determined to be 361 ± 17 cm^?1 (4.32 ± 0.20 kJ/mol). This stability order is consistent with that predicted by ab initio calculations but the ?H is much lower than the average energy value of 646 ± 73 cm^?1 obtained from the MP2 ab initio calculations or 611 ± 28 cm^?1 from the B3LYP density functional theory calculations. The percentage of the axial conformer present at ambient temperature is estimated to be 15 ± 1%. By utilizing previously reported microwave rotational constants for both conformers combined with ab initio MP2(full)/6–311+G(d,p) predicted structural values, adjusted r ₀ parameters have been obtained. The determined heavy atom structural parameters for the equatorial conformer are: the distances C–Cl = 1.783(5), C₁–C₄ = 1.539(3), C₄–C₆ = 1.558(3) Å, and angles ∠C₆C₄C₁ = 86.9(5), ∠C₄C₁C₅ = 89.7(5)°, and for the axial conformer are: the distances C–Cl = 1.803(5), C₁–C₄ = 1.547(3), C₄–C₆ = 1.557(3) Å, and angles ∠C₆C₄C₁ = 86.3(5), ∠C₄C₁C₅ = 88.9(5) and the puckering angles for the equatorial and axial conformers are 30.7(5)° and 22.3(5)°, respectively. The conformational stabilities, harmonic force fields, infrared intensities, Raman activities, depolarization ratios and vibrational frequencies have been obtained for both conformers from MP2(full)/6-31G(d) ab initio calculations and compared to experimental values where available. The results are discussed and compared to the corresponding properties of some similar molecules.